Other Assets - Unconsolidated Joint Ventures (Details) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2017 Garage	Dec. 31, 2017 building	Dec. 31, 2017 USD ($)
Equity Method Investments [Roll Forward]
Net LLC investment, beginning of period				$ 0
Equity income (loss) recognized during the period				7
Net LLC investments, end of period	$ 8,700			8,700
Parking Garages [Member]
Property, Plant and Equipment [Line Items]
Number of parking garages		2	2
Number of buildings acquired | building			3
Equity Method Investments [Roll Forward]
Net LLC investment, beginning of period				0
New investments during the period	8,700			8,700
Equity income (loss) recognized during the period				0
Net LLC investments, end of period	$ 8,700			$ 8,700